A heat exchanger, which comprises a plurality of heating tubes for carrying hot exhaust gas of the internal combustion engine, a plurality of cooling tubes for carrying a liquid cooling agent and a plurality of thermoelectric generators for generating an electric voltage from a temperature difference, wherein the thermoelectric generators are arranged each between such a heating tube and such a cooling tube, is known from DE 10 2010 022 225 A1. Furthermore, the heating tubes, thermoelectric generators and cooling tubes are arranged adjacent to each other in a stacking direction and form a stack.
A thermoelectric generator can convert a heat flux into an electric current or a temperature difference into an electric voltage by utilizing the so-called Seebeck effect. The Seebeck effect is based on an inversion of the Peltier effect. Such thermoelectric generators can therefore be used to recover heat or to generate electrical energy from heat and can be correspondingly used, e.g., in exhaust systems of internal combustion engines, preferably in motor vehicles, to improve the energy efficiency of the internal combustion engine or of the vehicle.
To improve the heat transfer between the thermoelectric generators and the heating and cooling tubes, it is, moreover, common practice to load the stack in the stacking direction with a force of pressure. To prevent the heating and cooling tubes from becoming indented in their cross sections in the process, a support structure, which braces the respective tube from the inside, is arranged in the heating and cooling tubes in the prior-art heat exchanger. Such a support structure may also be designed as a tube, i.e., as a support tube.